1. Field of the Invention
The present invention relates to a corneal endothelial cell measuring instrument for measuring cell density in a corneal endothelial cell image taken by using a specular microscope or the like.
2. Description of the Related Art
There are many kinds of methods of measuring the characteristics of corneal endothelial cells. A grid method is one of those known methods. As shown in FIGS. 4(a) and 4(b), in the grid method, a portion of a cell image is surrounded by a rectangle R of an optional size, then, the number N of cells included in the rectangle R are counted, and further, the number N of cells are divided by the area S of the rectangle R to determine a cell density CD. More specifically, when counting the number N of cells included in the rectangle R, the number of one cell entirely included in the rectangle R (i.e., nine cells P with a dot marked at their center in FIG. 4(b)) is counted as 1.0 respectively, and the number of one cell partly included in the rectangle R is counted as 0.5 respectively, regardless of the size of the portion included in the rectangle R.
When counting the number of the cells according to the grid method, the operator must decide whether the cell is included entirely in the rectangle R or the cell is included partly in the rectangle R, which takes a long time for measurement.
It often occurs that cells having only a very small portion cut by the side of the rectangle R are mistaken for those entirely included in the rectangle R and cells having a very small portion included in the rectangle R are overlooked, which reduces the accuracy of measurement.